The present invention relates generally to electrical outlet boxes and the like, and, more particularly, to cable clamp means formed integrally with an electrical outlet box, for securing an insulated electrical cable therein, as well as to closure means for cable entry ports.
It will be understood that although the present invention is described with particular reference to electrical outlet boxes which are adapted to house the termination (i.e., electrical connection) between an electrical power cable and an electrical fixture such as an electrical outlet receptacle or an electrical switch, the present invention can be adapted, where desired, for use in other housings for electrical distribution appliances, such as electrical junction boxes, flush type boxes, etc. Accordingly, when used herein, the term "electrical outlet box" is intended to embrace such additional structures.
The usual electrical outlet box is constructed in a generally box-like configuration with a generally continuous sidewall member depending from a back (or bottom) wall, and formed with one or more openings (usually referred to as "knockout windows") in the sidewall member, which are adapted to permit access to the interior of the box by electrical cables. Accordingly, one or more electrical power cables are inserted into the box, each through a knockout window, for connection to (or termination with) the electrical fixture to be mounted in the box. Moreover, in order to prevent debris from entering the box through knockout windows that are not utilized, and to minimize fire spread if the electrical appliance housed in the box malfunctions, the windows are closed by knockout panels which are removably attached to the box, across each window.
However, in some applications, it has been found that the connection between the electrical conductors and the electrical appliance may be stressed or dangerously loosened by forces exerted on the cable at other locations during installation. In addition, during construction of the structure in which the outlet box is installed, the cable is inserted through a knockout window after the box is mounted in place, but the electrical appliance may not be connected to the cable and installed in the box until after the wall board is secured in place. The cable is thereby susceptible to accidental removal from the knockout windows before it can be connected to the appliance, and a significant effort may be required to reinsert the cable into the box.
Threfore, in order to fixedly retain the cable in the box for preventing such stressing on the connections or for preventing removal from the knockout window, clamping devices have been developed, which are secured in or adjacent each knockout window opening and are adapted to grasp the cable firmly for preventing withdrawal from the box. In fact, such clamping devices are presently required by the National Electric Code for multigang boxes and for so-called "old-work" boxes.
Presently, most cable clamping devices are formed as independent structures which have to be fabricated separately from the box itself, in relatively complicated structures, such as shown in U.S. Pat. Nos. 3,788,582 issued to Swanquist, and 3,493,205 issued to Bromberg. These structures, therefore, involve substantial fabrication costs over and above those making the box alone. In addition, since the clamping devices have to be affixed to the box, they also entail additional installation time and consequent expense. Moreover, in order to be fixedly secured in the knockout window of the box, the engaging means for the device must be proportioned to fit the particular configuration of the knockout window. Thus, unless all knockout window proportions are standardized, numerous sized and/or shaped devices are needed, thereby greatly increasing the costs for making them.
Although there are some electrical outlet boxes which have cable clamping means formed integrally with the box, such as U.S. Pat. No. 3,112,938 issued to Karlin, the clamping structures themselves do not automatically grasp the cable once the knockout window closure means has been removed. Rather, several manipulative steps are necessary in order to assemble the clamping structure. Thus, it is possible to erect the clamping structure with too large of a space between its cable grasping edges so that clamping is not effected, thereby necessitating more manipulation to establish the proper spacing between the clamping edges.
In addition, heretofore, the knockout windows have usually been closed by planar closure panels which are structurally independent of the clamping device. Although the panels perform their intended function satisfactorily, they must first be removed before the cable can be inserted into the box, thereby necessitating a two-step operation.
Accordingly, it is an object of the present invention to provide new and improved cable clamp means for electrical outlet boxes and the like. It is also an object of the present invention to provide new and improved closure means for cable entry ports in electrical outlet boxes and the like.
It is another object of the present invention to provide new and improved cable clamp means for electrical outlet boxes and the like, which automatically grasp virtually any size electrical cable.
It is an additional object of the present invention to provide new and improved cable clamp means as well as new and improved closure means for cable entry ports in electrical outlet boxes and the like, which can be relatively easily and inexpensively formed integrally with the box.
It is a further object of the present invention to provide new and improved cable clamp means for electrical outlet boxes and the like, adapted to include closure means for preventing access through the cable entry ports.
It is still another object of the invention to provide new and improved cable clamp means for electrical outlet boxes and the like, including closure means formed as part thereof, which can be opened simply by forcefully striking the end of the electrical cable thereagainst.
It is an additional object of the present invention to provide new and improved closure means for cable entry ports electrical outlet boxes and the like, which can be opened simply by forcefully striking the electrical cable against the closure means.
It is yet another object of the present invention to provide new and improved cable clamp means for electrical outlet boxes and the like, which can be formed integrally with the box yet permit conventional knockout window closure panels to be formed integrally with the box.
Objects and advantages of the invention are set forth in part above and in part below. In addition, these and other objects and advantages will become apparent herefrom, or may be appreciated by practice with the invention, the same being realized and attained by means of the instrumentalities, combinations and structures pointed out in the appended claims. Accordingly, the present invention resides in the novel parts, constructions, arrangements, improvements and structures herein shown and described.